The present invention relates to computer controlled bar code scanners and, more particularly, to an interface which permits such scanners to be controlled by and transfer data to a personal computer.
Laser scanners are known in which a beam of laser light is swept in a scan pattern to find and read a bar code. The bar code is printed on a surface which is presented to the scanner, such as for example a package label. Bar code labels are used on a broad range of retail packages for check-out and inventory purposes. A scanner, located for example at the check-out station in a retail establishment, is used by a clerk to enter automatically product identification data into the host computer of an associated computer system. The host computer then totals the prices of the products purchased by a customer, computes any applicable taxes, and causes a cash register printer associated with the scanner to print a receipt. The computer system keeps accurate records of sales by specific product which permit desired inventory levels to be maintained.
Typically such a scanner includes a laser source, such as a gas discharge laser, which produces a low power laser beam. The beam then passes through appropriate optical lenses and is swept across the package surface by a motor-driven, rotating mirror assembly. A portion of the light reflected from the package surface returns through the optical lenses to a detector which provides an electrical signal in dependence upon the level of the reflected light. A signal processing system in the scanner then analyses the electrical signal and translates the scanned characters into data which is transmitted to the host computer.
The computer then determines the total price of the products being purchased, as well as storing the identity of the purchased products for inventory and accounting purposes. The host computer may be located in the cash register associated with the scanner. Alternatively, a single host computer may service a number of scanners at the retail establishment.
Typically, the host computer in such a scanner system is a large, mainframe computer which is capable of servicing simultaneously a large number of scanners. Such a computer will include specially designed interface circuitry which permits the host computer to function in this fashion. A need exists, however, for much smaller point of sale scanner systems in which the scanner is coupled to a personal computer. In a small retail establishment, for example, only a single scanner may be needed at the store's sole check-out location. Clearly, the computing power of a personal computer is more than adequate for such a point of sale system. A need exists, however, for an interface arrangement which is carried on a single circuit board configured to be inserted directly into an expansion slot of a personal computer.